1. Field of the Invention
The present invention relates generally to a method and apparatus for brain perfusion magnetic resonance imaging (MRI) technique, and more particularly, to a method and apparatus for brain perfusion MRI technique with removal of cerebrospinal fluid (CSF) pixels using a CSF/brain-contrast-enhanced image and a segmentation technique.
2. Background
Brain perfusion MRI technique is used for the diagnosis of cerebrovascular diseases such as stroke and stenosis. Traditional tracer kinetic models for intravascular agents can be extended to dynamic susceptibility contrast MRI data to calculate cerebral blood volume (CBV), cerebral blood flow (CBF), and tracer mean transit time (MTT). According to the central volume theorem, MTT=CBV/CBF. In a dynamic-susceptibility-contrast perfusion MRI study, a bolus of contrast agents is injected through an antecubital vein and a series of dynamic images are acquired from the patient's brain to record the passage of contrast agents. Parametric images such as time to peak (TTP) of the concentration-time curve and MTT can be calculated from the dynamic images to reveal local perfusion at brain tissues. Tissues with hyperintensity on either TTP or MTT images have delayed blood perfusion and they are at risk of infarction. These two parametric images are valuable for the diagnosis and treatment planning of cerebrovascular diseases. However, CSF also appears hyperintensity on these two parametric images and CSF may interfere with quantitative measurements on the extent of tissues with delayed perfusion. Therefore, the identification and removal of CSF pixels on perfusion parametric images can improve the measurements on the area of tissue with delayed perfusion.
U.S. Pat. No. 6,546,275, issued to Carroll et al. entitled “Determination of the arterial input function in dynamic contrast-enhanced MRI” discloses that a contrast-enhanced MRI time course study of the brain is performed and images are produced which indicate hemodynamic parameters such as CBF, CBV and MTT. An arterial input function required to quantitatively measure the hemodynamic parameters is automatically produced.
U.S. Pat. No. 7,020,578, issued to Sorensen et al. entitled “Method for evaluating novel, stroke treatments using a tissue risk map” discloses that a method of evaluating stroke treatments includes generating a risk map indicative of the probability of tissue infarction on voxel-by-voxel basis and selecting a probability range for evaluating the therapeutic effect of the treatment. In one particular embodiment, tissue having a fifty percent probability of tissue infarction is selected. A treatment that has a reduced level of overall actual infarction as compared to the predicted value is indicative of therapeutic effect.
U.S. Pat. No. 7,069,068, issued to Ostergaard et al. entitled “Method for determining haemodynamic indices by use of tomographic data” discloses that haemodynamic indices of an organ or a part of tissue are determined from a time series of tomographic data obtained by means of MRI. Maps of indices are produced, being significant of the dynamics of the capillary tissue flow acquired during rapid bolus injection of a tracer that stays mainly intravascular. The method may be used for evaluating the efficacy of a drug on an organ, or for obtaining information of the likelihood of recovery of an organ or part of tissue upon or during a period of insufficient vascular supply or during the progression of a chronic disease. The method may be used for discriminating between relevant therapy of an organ.
U.S. Pat. No. 7,512,435, issued to Wu et al. entitled “Delay-compensated calculation of tissue blood flow” discloses that methods for computing perfusion parameters are described. The methods are typically used to analyze MR images and other image data and to calculate tissue perfusion parameters such as CBF in the brain or in tissues in other organs such as the heart. The methods employ a block-circulant matrix for deconvolving the perfusion parameters from the image data.
U.S. Pat. No. 7,580,737, issued to Wintermark et al. entitled “Method and apparatus for determining treatment for stroke” discloses that a method and apparatus for evaluating acute stroke patients and for determining whether a stroke patient will benefit from the use of thrombolysis therapy includes obtaining measurements of the CBF and CBV of the brain of a stroke patient, determining ischemic areas of the brain where the ischemic areas comprise the measurements of CBF which are less than a first value and creating a penumbra-infarct map of the ischemic areas of the brain using the measurements. The infarct area corresponds to the area of the brain where CBV is less than a second value. The penumbra area corresponds to the area of the brain where CBV is greater than this second value. The method also includes determining a ratio of penumbra size to the total of penumbra size and infarct size. When the ratio is greater than a predetermined value, the stroke patient is a candidate for thrombolysis therapy.
However, the above disclosures do not effectively remove the CSF pixels on brain perfusion parametric images to improve the measurements on the area of tissue with delayed perfusion. According above problems, it needs a method and apparatus to overcome the disadvantage of the prior art.